Resonant structures, acoustic resonators, acoustic filters

Abstract

The present application relates to the field of semiconductor technology, and discloses a resonant structure, including: a piezoelectric layer; an upper electrode layer, arranged on one side of the piezoelectric layer; a lower electrode layer, arranged on the other side of the piezoelectric layer; an isolation ring, surrounding the part of the piezoelectric layer in the effective working area; the effective working area is the overlapping area of ​​the first projection and the second projection; the first projection is the positive projection of the upper electrode layer on the piezoelectric layer, and the second projection is the positive projection of the lower electrode layer on the piezoelectric layer. The resonant structure can improve the quality factor of the acoustic resonator. The present application also discloses an acoustic resonator and an acoustic filter.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, for example, to a resonant structure, an acoustic resonator, and an acoustic filter. Background Art

[0002] With the rapid development of communication technology, the application and demand of RF filters are constantly upgrading. The operating frequency of RF filters is getting higher and higher, the bandwidth is getting wider and wider, the insertion loss is getting lower and lower, and the overall performance requirements of RF filters are getting higher and higher. In the prior art, RF filters are often composed of one or more coupled acoustic resonators. Acoustic resonators are devices used to realize the mutual conversion of electrical energy and mechanical energy. They play an important role in the field of RF communication and sensing. Therefore, the performance improvement of acoustic resonators is of great significance to the performance improvement of communication systems.

[0003] In order to obtain a highly integrated, planar, and easily packaged radio frequency filter, the existing technology usually adopts the method of depositing multiple resonant structures on the same substrate. Existing bulk acoustic wave resonators generally have lateral parasitic noise, which affects the performance of the resonator.

[0004] The quality factor of an acoustic resonator is one of the key indicators that affect its performance. Therefore, how to reduce the lateral acoustic wave leakage in the resonator to improve the quality factor of the acoustic resonator has become a technical problem that needs to be solved urgently.

[0005] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present application, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0006] In order to provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. The summary is not an extensive review, nor is it intended to identify key / critical elements or delineate the scope of protection of these embodiments, but rather serves as a prelude to the detailed description that follows.

[0007] The embodiments of the present disclosure provide a resonant structure that can effectively suppress transverse mode parasitic noise.

[0008] In some embodiments, the resonant structure includes: a piezoelectric layer; an upper electrode layer, arranged on one side of the piezoelectric layer; a lower electrode layer, arranged on the other side of the piezoelectric layer; an isolation ring, surrounding the portion of the piezoelectric layer that is in an effective working area; the effective working area is an overlapping area of ​​the first projection and the second projection; the first projection is an orthographic projection of the upper electrode layer on the piezoelectric layer, and the second projection is an orthographic projection of the lower electrode layer on the piezoelectric layer.

[0009] In some embodiments, the top electrode layer is made of one or more of molybdenum, aluminum, copper, platinum, tantalum, tungsten, palladium and ruthenium.

[0010] In some embodiments, the lower electrode layer is made of one or more of molybdenum, aluminum, copper, platinum, tantalum, tungsten, palladium and ruthenium.

[0011] In some embodiments, the piezoelectric layer is made of any one of aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lithium niobate, and lithium tantalate.

[0012] In some embodiments, the isolation ring is made of a material that avoids the generation of a conductive channel.

[0013] In some embodiments, the acoustic velocity of the isolation ring is not equal to the acoustic velocity of the piezoelectric layer.

[0014] In some embodiments, the isolation ring is made of resin; or, the isolation ring is made of AlN; or, the isolation ring is made of SiO 2 Made of; or, the isolation ring is an air ring.

[0015] In some embodiments, the thickness of the isolation ring is the same as the thickness of the piezoelectric layer.

[0016] In some embodiments, an acoustic resonator including the above-mentioned resonant structure is also provided.

[0017] In some embodiments, an acoustic filter including the above-mentioned acoustic resonator is also provided.

[0018] The resonant structure, acoustic resonator, and acoustic filter provided by the embodiments of the present disclosure can achieve the following technical effects:

[0019] By using an isolation ring to surround the portion of the piezoelectric layer in the effective working area, the boundary effect of the effective working area is reduced, and the lateral parasitic noise is suppressed, thereby facilitating the improvement of the quality factor of the acoustic resonator.

[0020] The above general description and the following description are exemplary and explanatory only and are not intended to limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] One or more embodiments are exemplarily described by corresponding drawings, which do not limit the embodiments. Elements with the same reference numerals in the drawings are shown as similar elements, and the drawings do not constitute a scale limitation, and wherein:

[0022] Figure 1 is a schematic diagram of a resonant structure provided by an embodiment of the present disclosure;

[0023] Figure 2 is a top view of a piezoelectric layer and an isolation ring provided by an embodiment of the present disclosure;

[0024] Figure 3is a schematic diagram of an acoustic resonator provided by an embodiment of the present disclosure;

[0025] Figure 4 It is a curve diagram of the operating frequency freq.GHz and the quality factor Q of a disclosed embodiment. DETAILED DESCRIPTION

[0026] In order to be able to understand the features and technical contents of the embodiments of the present disclosure in more detail, the implementation of the embodiments of the present disclosure is described in detail below in conjunction with the accompanying drawings. The attached drawings are for reference only and are not used to limit the embodiments of the present disclosure. In the following technical description, for the convenience of explanation, a full understanding of the disclosed embodiments is provided through multiple details. However, one or more embodiments can still be implemented without these details. In other cases, to simplify the drawings, well-known structures and devices can be simplified for display.

[0027] The terms "first", "second", etc. in the specification and claims of the embodiments of the present disclosure and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so that the embodiments of the embodiments of the present disclosure described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0028] Unless otherwise stated, the term "plurality" means two or more.

[0029] In the embodiment of the present disclosure, the character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B indicates: A or B.

[0030] The term "and / or" is a description of the association relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or, A and B.

[0031] The term "correspondence" may refer to an association relationship or a binding relationship. The correspondence between A and B means that there is an association relationship or a binding relationship between A and B.

[0032] Combination Figure 1 As shown, an embodiment of the present disclosure provides a resonant structure, including: a piezoelectric layer 1, an upper electrode layer 2, a lower electrode layer 3 and an isolation ring 4. The upper electrode layer 2 and the lower electrode layer 3 are respectively arranged on two sides of the piezoelectric layer, and the upper electrode layer 2, the piezoelectric layer 1 and the lower electrode layer 3 overlap with each other to form an effective working area. The isolation ring 4 surrounds the part of the piezoelectric layer that is in the effective working area. Among them, the effective working area is the overlapping area of ​​the first projection and the second projection. The first projection is the positive projection of the upper electrode layer on the piezoelectric layer, and the second projection is the positive projection of the lower electrode layer on the piezoelectric layer. The isolation ring 4 is located between the upper electrode layer 2 and the lower electrode layer 3.

[0033] By adopting the packaging structure provided in the embodiment of the present disclosure, the portion of the piezoelectric layer in the effective working area is surrounded by an isolation ring, thereby reducing the boundary effect of the effective working area and suppressing lateral parasitic noise, thereby facilitating the improvement of the quality factor of the acoustic resonator.

[0034] Optionally, the upper electrode layer is made of one or more of molybdenum, aluminum, copper, platinum, tantalum, tungsten, palladium and ruthenium.

[0035] Optionally, the lower electrode layer is made of one or more of molybdenum, aluminum, copper, platinum, tantalum, tungsten, palladium and ruthenium.

[0036] Optionally, the piezoelectric layer is made of any one of aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lithium niobate and lithium tantalate.

[0037] Optionally, the isolation ring is made of insulating material.

[0038] Optionally, the isolation ring is an annular isolation cavity, that is, the isolation ring is an air ring.

[0039] Optionally, the isolation ring is made of a material that avoids the generation of a conductive channel.

[0040] Optionally, the acoustic velocity of the isolation ring is not equal to the acoustic velocity of the piezoelectric layer.

[0041] Optionally, the isolation ring is made of resin.

[0042] Optionally, the isolation ring is made of aluminum nitride AlN.

[0043] Optionally, the isolation ring is silicon dioxide SiO 2 Made.

[0044] Optionally, the thickness of the isolation ring is the same as the thickness of the piezoelectric layer.

[0045] Table 1 shows the quality factor and effective electromechanical coupling coefficient of the isolation ring of different materials. As shown in Table 1, due to the setting of the isolation ring, the resonant structure sacrifices a certain effective electromechanical coupling coefficient keff2, and improves the resonator quality factor. Series_Q in Table 1 is the series resonance quality factor. Parallel_Q in Table 1 is the parallel resonance quality factor. Figure 4 The horizontal axis is the operating frequency of the resonant structure, and the vertical axis is the quality factor. Figure 4It can be seen that among aluminum nitride, air, resin and silicon dioxide, resin has the best performance as an isolation ring. According to the Bode curve of the quality factor, it can be seen that the quality factor of resin and air is higher. The series quality factor of resin is 1691.1, which is 26.9% higher than that of aluminum nitride 1332.65; the higher the quality factor, the better; Keff2 is related to the bandwidth of the filter. The larger the bandwidth, the larger the corresponding Keff2, otherwise it is difficult to achieve the large bandwidth requirement. For filters with small bandwidth, if Keff2 is too large, it is difficult to achieve the narrowband frequency selection requirements. Therefore, the value of Keff2 is selected according to the filter bandwidth requirements.

[0046]

[0047] Table 1

[0048] like Figure 2 As shown, the effective working area of ​​the piezoelectric layer 1 is a pentagon, and the isolation ring 4 is also set to a pentagon. In some embodiments, the isolation ring is made by etching the piezoelectric layer along the thickness direction of the piezoelectric layer to form an annular gap on the piezoelectric layer, and filling the annular gap with an insulating material to form an isolation ring, which surrounds the piezoelectric layer. In some embodiments, the piezoelectric layer is provided with multiple isolation rings according to the requirements of setting the resonator.

[0049] The embodiment of the present disclosure also provides an acoustic resonator, which includes the above-mentioned resonance structure. Optionally, the acoustic resonator is a bulk acoustic wave resonator or a thin film bulk acoustic wave resonator.

[0050] Combination Figure 3As shown, in some embodiments, the acoustic resonator includes a substrate 5, a cavity 6 formed in the substrate, and a resonant structure. The resonant structure includes: a piezoelectric layer 1, an upper electrode layer 2, a lower electrode layer 3 and an isolation ring 4. The upper electrode layer 2 and the lower electrode layer 3 are respectively arranged on both sides of the piezoelectric layer 1, and the upper electrode layer 2, the piezoelectric layer 1 and the lower electrode layer 4 overlap each other to form an effective working area. The isolation ring 4 surrounds the part of the piezoelectric layer 1 that is in the effective working area. Among them, the effective working area is the overlapping area of ​​the first projection and the second projection. The first projection is the positive projection of the upper electrode layer on the piezoelectric layer, and the second projection is the positive projection of the lower electrode layer on the piezoelectric layer. The substrate is arranged on the side of the resonant structure with the lower electrode layer, and the lower electrode layer is located in the cavity, and the cavity can reflect the sound wave energy in the thickness direction of the bulk acoustic resonator back to the bottom electrode. The overlapping area of ​​the cavity, the lower electrode layer, the piezoelectric layer and the upper electrode layer in the stacking direction forms an effective resonance area, and the area of ​​the overlapping area is the area of ​​the overlapping area of ​​the positive projection of the cavity, the lower electrode layer, the piezoelectric layer and the upper electrode layer on the substrate. When the input electrical signal is applied between the upper electrode and the lower electrode, the reverse piezoelectric effect causes the piezoelectric layer to mechanically expand or contract due to the polarization of the piezoelectric material. When the input electrical signal changes with time, the expansion and contraction of the piezoelectric layer excites sound waves, which are converted into electrical signals through the piezoelectric effect.

[0051] By using an isolation ring to surround the portion of the piezoelectric layer in the effective working area, the boundary effect of the effective working area is reduced, and the lateral parasitic noise is suppressed, so that the quality factor of the acoustic resonator is higher, and the coupling between adjacent inductors can be effectively reduced or eliminated.

[0052] The embodiment of the present disclosure also provides an acoustic filter, which includes a plurality of resonators connected in series and / or in parallel, at least one of which is the above-mentioned acoustic resonator. Optionally, the acoustic filter is a bulk acoustic wave filter or a thin film bulk acoustic wave filter.

[0053] The above description and the accompanying drawings sufficiently illustrate the embodiments of the present disclosure to enable those skilled in the art to practice them. Other embodiments may include structural and other changes. The embodiments represent only possible variations. Unless explicitly required, individual components and functions are optional, and the order of operations may vary. Portions and features of some embodiments may be included in or replace portions and features of other embodiments. The embodiments of the present disclosure are not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A resonant structure, characterized in that: include: Piezoelectric layer; An upper electrode layer, arranged on one side of the piezoelectric layer; A lower electrode layer is disposed on the other side of the piezoelectric layer, and an effective working area of ​​the lower electrode layer is configured to be located in a cavity formed in a substrate of the acoustic resonator, wherein the substrate is disposed on a side of the resonant structure having the lower electrode layer; an isolation ring, surrounding the portion of the piezoelectric layer in the effective working area, the thickness of the isolation ring being the same as the thickness of the piezoelectric layer, and the isolation ring being located between the upper electrode layer and the lower electrode layer; the effective working area being the overlapping area of ​​the first projection and the second projection; the first projection being the orthographic projection of the upper electrode layer on the piezoelectric layer, and the second projection being the orthographic projection of the lower electrode layer on the piezoelectric layer; The isolation ring is manufactured in the following manner: the piezoelectric layer is etched along the thickness direction of the piezoelectric layer to form an annular gap on the piezoelectric layer, and the annular gap is filled with an insulating material to form the isolation ring.

2. The resonant structure according to claim 1, characterized in that: The upper electrode layer is made of one or more of molybdenum, aluminum, copper, platinum, tantalum, tungsten, palladium and ruthenium.

3. The resonant structure according to claim 1, characterized in that: The lower electrode layer is made of one or more of molybdenum, aluminum, copper, platinum, tantalum, tungsten, palladium and ruthenium.

4. The resonant structure according to claim 1, characterized in that: The piezoelectric layer is made of any one of aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lithium niobate and lithium tantalate.

5. The resonant structure according to claim 1, characterized in that: The isolation ring is made of a material that avoids the generation of a conductive channel.

6. The resonant structure according to claim 5, characterized in that: The acoustic velocity of the isolation ring is not equal to the acoustic velocity of the piezoelectric layer.

7. The resonant structure according to claim 6, characterized in that: The isolation ring is made of resin; or, the isolation ring is made of AlN; or, the isolation ring is made of SiO2; or, the isolation ring is an air ring.

8. An acoustic resonator, characterized in that: A resonant structure comprising a substrate, a cavity formed in the substrate, and a resonant structure according to any one of claims 1 to 7; The substrate is arranged on a side of the resonant structure having a lower electrode layer, and the lower electrode layer is located in the cavity.

9. An acoustic filter, characterized in that: Comprising at least one acoustic resonator as claimed in claim 8.

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